The present invention relates to a radiography system, or more particularly, to a radiography system that is ranged on a subject using light prior to X-irradiation.
Radiography systems are ranged on a subject using light prior to X-irradiation. After a radiography system is ranged, X-rays are irradiated. Consequently, an irradiated position to which X-rays that are an invisible radiation are irradiated can be checked in advance using a visible radiation (refer to, for example, Patent Document 1).
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 55-115001 (pp. 1, FIG. 1)
In order to check a field of view (FOV) in an X-ray field in advance, light is irradiated through a collimator for X-rays. In this case, a light source must be accurately positioned with respect to a focal spot of X-rays. However, the light source may be displaced due to the effect of tolerances of components. In this case, an FOV in a light field disagrees with an FOV in an X-ray field. A radiography system cannot be ranged accurately.